The present invention relates to a catalyst element for cleaning exhaust gases, and is particularly suitable for, but not limited to, a device for cleaning the exhaust gases of an internal combustion engine in cooperation with another exhaust gas cleaning device.
The exhaust gases discharged from internal combustion engines contain pollutants very harmful to human health, and their emission is limited by laws, orders and regulations. In general, the pollutants are carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx) and so on, and in order to remove them, catalytic oxidation and reduction have been long used to convert them into carbon dioxide (CO.sub.2), water (H.sub.2 O), nitrogen (N.sub.2) and so on, and a wide variety of catalysts and catalyst type exhaust gas cleaning devices have been devised and demonstrated.
Heretofore, pellet, bead and monolithic type catalyst devices have been used for cleaning internal combustion engine exhaust gases. However, there is need for a catalyst device which exhibits flexibility, resistance to high temperatures, and which is simple in construction.
An object of the present invention is to provide an auxiliary catalyst element which is simple in construction yet very effective in removing pollutants in the exhaust gases of an internal combustion engine. Such an element may be placed upstream of a main catalytic type exhaust gas cleaning device (the "main catalyst") so that the combination of the main and auxiliary catalyst elements may provide a high exhaust gas cleaning rate while minimizing thermal degradation of the catalytic performance of said devices.
As herein described, there is provided a catalyst element for cleaning exhaust gases, comprising a heat resistant metal member having a cylindrical shape, a web of heat resistant inorganic fibers supported by said member, and a layer of catalyst material disposed on said web.